Venus and Mars are planetary opposites. One is hot; the other, cold. One has a thick atmosphere; the other, not much atmosphere at all. Even their names are opposites. Venus is named for the Roman goddess of love and beauty, while Mars bears the name of the god of war. Right now, they do share a location — close together in the west at nightfall.

Venus and Mars flank Earth. Venus is the next planet in toward the Sun, with Mars the next planet out. Venus is about the size of Earth, with Mars a little more than half that big.

The combination of location and size explains the differences.

Because Venus is bigger and heavier, its gravity is stronger. That allowed it to hang on to its early atmosphere. With the Sun so close, that made the planet hotter. The extra heat evaporated any water Venus might’ve had, and baked gases out of its rocks. That made the atmosphere thicker, trapping more heat. Today, the atmosphere is more than 90 times as dense as Earth’s, and it’s hot enough to melt lead.

Mars, on the other hand, is small and light, so its gravity is weak. That allowed much of its atmosphere to leak into space, making the planet colder. Today, the air is less than one percent as thick as Earth’s, and Mars is almost always far below freezing.

Venus blazes as the “evening star,” with fainter Mars close to its upper left. They’ll stay close for a few more nights, then start to move apart — putting some distance between planetary opposites.
 

Script by Damond Benningfield

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